Unfortunately, prolongation of life in AIDS sufferers may lead to a higher incidence of AIDS-related cognitive deficits. It is, therefore, extremely important to develop an animal model of human AIDS-related cognitive impairment. A neurotropic variant of SIV is being tested in pigtail macaques that have been trained on a battery of cognitive tasks. If this variant produces cognitive deficits, then the SIV-infected pigtail macaque may provide the needed model for future studies of possible treatments of AIDS-related dementias.